The present disclosure relates to a edge-emitting laser diode.
In recent years, a blue-violet laser diode using a nitride compound semiconductor is widely used as a light source for a high-capacity optical disk, and a very-reliable device with a higher output is being developed. In an edge emitting laser diode of this kind, however, induced emission occurs strongly in the center of an NFP (Near Field Pattern) where the light emission intensity is the highest. Consequently, a phenomenon (hole burning) that carriers injected in the center of the NFP recombine particularly quickly and gain is saturated occurs. When such a hole burning phenomenon occurs, the horizontal transverse mode becomes unstable, it causes decrease in the kink level in the L-I (Light output-Injection current) characteristic. Such a drawback occurs not only in a laser diode of a gain guide structure but also in a laser diode of an index guide structure. Therefore, when the kink level decreases, a stable high-output laser diode is not realized.
As a method of stabilizing the horizontal transverse mode, two methods are employed in a ridge laser diode. In the first method, by decreasing the width of a stripe (current path), carriers are diffused from the end of the stripe to a center part to thereby suppress hole burning. In the second method, by increasing a light loss on the side of the ridge, a high-order horizontal transverse mode is prevented from having a gain.